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As of early Wednesday morning, Hurricane Florence had weakened slightly with sustained winds of 130mph, but this is of little consequence as the track forecast now shows a dangerous stalling out near the coast, or just onshore by late Thursday or Friday morning. This will exacerbate already extremely heightened concerns about inland flooding due to torrential rainfall from Florence.

Hurricanes produce three major kinds of threats: storm surge, damaging winds, and inland flooding from rainfall. Most hurricanes produce a combination of the above with varying severity, but rarely does a hurricane present all three threats at an extreme level. Florence is such a hurricane, with what the National Hurricane Center characterizes as a "life-threatening" storm surge for portions of the North and South Carolina coast and "damaging" winds for these same coastal areas. (See warning areas.)

Further Reading

However, probably the biggest concern with Florence is inland flooding, especially as the storm is now likely to become nearly stationary along the Carolina coast and then slowly trudge inland. Adding to these concerns is a new twist the forecast models are indicating will happen—a southwestward jog toward Georgia.

This should only amplify rainfall totals as the storm's core remains offshore, with access to warm Atlantic waters to regenerate rain-making bands of precipitation. Texas saw a similar scenario in 2017, when Hurricane Harvey's center moved just inland, and its counter-clockwise rotation allowed the storm to continually pull moisture inland from the Gulf of Mexico.

The southwest jog

As recently as Monday morning, hurricane models were forecasting a fairly conventional landfall for Florence, bringing the storm to the coast before bringing it slowly inland on a generally northwestward track. However, recent trends in the forecast models now indicate a rare—if not unprecedented for an Atlantic hurricane this far north and west—turn to the southwest before Florence resumes its west-northwest motion.

This change in track can be discerned from the ensemble forecast from the European model initialized at 8am Monday (12:00 UTC) on the left in the image below, and the European model initialized at 8pm Tuesday (00:00 UTC Wednesday). Ensemble forecasts capture the uncertainty in a forecast by initializing a computer model with slightly different starting conditions. It is striking that nearly all of the ensemble members now show a southwestern jog, which raises confidence in this forecast.

So what is causing this? A ridge of high pressure situated over the Central and Eastern United States is forecast to be a little stronger than anticipated, and this feature should force Florence to move around its periphery. As Florence trances the edge of this high pressure system, by later Friday or so, the atmospheric steering currents essentially break down.

Normally, when hurricanes get above 30 degrees North in latitude, they get pulled poleward by the westerly pattern in the atmosphere between the tropics and poles. However, because the aforementioned high pressure will be blocking a northward movement by Florence, this rapid turn to the north and eventually northeast will not happen for some time.

Major flooding event

All of this means that, in addition to very strong winds and storm surge beginning Thursday along the Carolina coasts, the southeastern United States will have to prepare for a major, and perhaps historic, flooding event.

It really is impossible to say where a "bullseye" will occur in terms of rainfall due to the uncertain storm motion, but coastal areas of the Carolinas likely face the greatest threat. Forecast modeling indicates broad areas may receive 10 to 30 inches of rain, with higher localized totals of 30 to 40 inches over the next week or so.

Enlarge/ NOAA's official rainfall forecast for the next seven days, released Wednesday morning, may undersell the higher localized risks. (Pivotal Weather)

It is worth noting that both the European and US Global Forecast System models forecast isolated totals of more than 40 inches. We cannot rule such extremes out should Florence stall out near the coast, or just inland. Needless to say, with soils already sodden in the southeast, this would present a dire scenario for inland flooding.

214 Reader Comments

The latest gfs shows the storm curving torwards the north east so Pennsylvania and new yorks rain totals might be more then that. The European model shows it going south with the gfs showing it going north.

There is an incredible amount of uncertainty in the track motions after 4-5 days due to the lack of steering currents as noted in the story.

The GFS model *is* now on board with the stall, then southwest jog in 3-4 days from now.

From the beginning the ECMWF had a Southern tendency and the GFS a Northern.

The models still have a separation but the GFS is now aligning closer to ECMWF and the NWS forcasts clearly show the result. Wind and rain predictions from Monday to Wednesday have major differences particularly for Western VA and Northern GA.

I also noticed that the NWS forecast discussions seemed much more tepid than previous. For Florence they did not venture far from the official run or point out the possible impact of longer term (5-6 days) trends.

The latest gfs shows the storm curving torwards the north east so Pennsylvania and new yorks rain totals might be more then that. The European model shows it going south with the gfs showing it going north.

There is an incredible amount of uncertainty in the track motions after 4-5 days due to the lack of steering currents as noted in the story.

The GFS model *is* now on board with the stall, then southwest jog in 3-4 days from now.

It is now. But do you think that maybe again the ECMWF model showed more accurate (in terms of where we are at 2 days) predictions 5 days out than the GFS?

The risk of flooding reminds me of a video that I recently watched about how rich cities are building high levees along rivers, which worsens the flooding for poorer cities with lower levees. I don't know exactly how widespread this problem is, but it probably deserves much more coverage than it gets.

In reply to the political comments above, let's wait until we see how this administration actually handles this disaster (and the inevitable, related articles) before hopping on the Trump Train, shall we...?

We can file this whole scenario under the "oh shit that's not good" category. The weather channel and others will often play up the drama of a storm for the same reasons newscasters play up political or criminal drama, but this thing is truly a monster, as the governor of N. Carolina stated yesterday.

If you're in the path of the core part of the storm early on, and in a low-lying area, don't be an idiot and try to "ride it out" — especially single story homes. With the stall and amount of rain forecast, you have a pretty good shot at ending up dead whether you cut a hole in the roof of your house or not. GTFO now.

Can we please stow the Trump crap for now? At least wait for his inevitable fuck up or clueless comment (great success in Puerto Rico doesn't count) before turning something that has nothing to do with Trump, into something that does. Tired of seeing that asshole's name everywhere I look.

Ok so now I feel bad. Over the last couple days I have gotten more and more relieved because the original tracks had it coming up through south eastern virginia. Each day the updated tracks pushed it further and further west which is a good thing for our area.

It stalling and meandering over the carolinas is going to create a world of hurt for people just south of us.

The latest gfs shows the storm curving torwards the north east so Pennsylvania and new yorks rain totals might be more then that. The European model shows it going south with the gfs showing it going north.

There is an incredible amount of uncertainty in the track motions after 4-5 days due to the lack of steering currents as noted in the story.

The GFS model *is* now on board with the stall, then southwest jog in 3-4 days from now.

It is now. But do you think that maybe again the ECMWF model showed more accurate (in terms of where we are at 2 days) predictions 5 days out than the GFS?

This time.

It could have been reversed, and has been numerous times.

The storm could even still end up heading north.

That's really the point here, There are an enormous amount of data points and levels of uncertainty that make the actual path nigh impossible to accurately predict.

The models can come close, but the longer out the prediction the greater the chance it will be wrong..

I was hoping it would hit the Mid-Atlantic instead of stalling, but instead it seems that it might turn north after destroying the coastal Carolina and still cause problems. Even after hitting the Carolinas this still could be on par with some of the worse hurricanes we've had up north.

Ugh. I live in upstate SC (upper left corner of the state on a map) and just the rain is going to be brutal. This is hilly terrain encompassing the lower end of the Blue Ridge mountains, with heavy Piedmont clay ultisol, that's already close to saturated with our normal amount of rainfall so far. I work in the foothills and lower mountains frequently and I know many valleys and river banks are going to be drowned. Wouldn't surprise me at all if several bridges I go over regularly get washed out. The coastal areas are all rightly concerned about the direct damage by wind, flooding, and storm surges (not to mention erosion of the extremely desirable sandy beaches and barrier islands). But inland flooding is going to be an issue in all corners of the Carolinas.

“Sen. Jeff Merkley released a document Tuesday showing a transfer of nearly $10 million from the Federal Emergency Management Agency to US Immigration and Customs Enforcement, and accused President Donald Trump's administration of diverting funds from hurricane relief just as hurricane season approaches.”

Trump’s malicious and malevolent admin has cost lives...and will cost more lives as we all witness this next unfolding disaster.

NHC's satellite imagery has gotten so impressive over the last 10 years or so. It's always been cool (with a side-helping of scary in this case), but

I repeat: if you're in a low-lying area and on the projected path of the storm in the Thursday / Friday timeframe, leave now and don't just go stay with your cousin 50 miles away. You need to take a road trip.

The Republican North Carolina legislature banned the use of climate change science in state disaster planning because they thought it would harm the state economically. Category 5 irony heading their way.

We can file this whole scenario under the "oh shit that's not good" category. The weather channel and others will often play up the drama of a storm for the same reasons newscasters play up political or criminal drama, but this thing is truly a monster, as the governor of N. Carolina stated yesterday.

If you're in the path of the core part of the storm early on, and in a low-lying area, don't be an idiot and try to "ride it out" — especially single story homes. With the stall and amount of rain forecast, you have a pretty good shot at ending up dead whether you cut a hole in the roof of your house or not. GTFO now.

Is Jim Cantore there yet? If he is, then we know they’re really in trouble.

The Republican North Carolina legislature banned the use of climate change science in state disaster planning because they thought it would harm the state economically. Category 5 irony heading their way.

I know it is probably impossible for a storm of this magnitude to leave the region without causing enormous levels of damage and hardship for the residents of the Southeast.

I hope the people of the region recognize the danger confronting them, are willing and able to follow the sound advice of the evacuation orders, and head for safety.

The only good news we could expect from this highly destructive event would be to read that no one was killed. Sadly, not everyone is either willing or able to get out of the way. All we can do is brace ourselves for the inevitable.

We can file this whole scenario under the "oh shit that's not good" category. The weather channel and others will often play up the drama of a storm for the same reasons newscasters play up political or criminal drama, but this thing is truly a monster, as the governor of N. Carolina stated yesterday.

If you're in the path of the core part of the storm early on, and in a low-lying area, don't be an idiot and try to "ride it out" — especially single story homes. With the stall and amount of rain forecast, you have a pretty good shot at ending up dead whether you cut a hole in the roof of your house or not. GTFO now.

Is Jim Cantore there yet? If he is, then we know they’re really in trouble.

We can file this whole scenario under the "oh shit that's not good" category. The weather channel and others will often play up the drama of a storm for the same reasons newscasters play up political or criminal drama, but this thing is truly a monster, as the governor of N. Carolina stated yesterday.

If you're in the path of the core part of the storm early on, and in a low-lying area, don't be an idiot and try to "ride it out" — especially single story homes. With the stall and amount of rain forecast, you have a pretty good shot at ending up dead whether you cut a hole in the roof of your house or not. GTFO now.

Is Jim Cantore there yet? If he is, then we know they’re really in trouble.

Top story on google news’ website; even through proxies and cognito mode. Grats Ars. Ive been a fan of your deeper intellectual journalism for so many years. It’s great to see y’all get this much exposure.

NHC's satellite imagery has gotten so impressive over the last 10 years or so. It's always been cool (with a side-helping of scary in this case), but

I repeat: if you're in a low-lying area and on the projected path of the storm in the Thursday / Friday timeframe, leave now and don't just go stay with your cousin 50 miles away. You need to take a road trip.

If you're in the path of the core part of the storm early on, and in a low-lying area, don't be an idiot and try to "ride it out" — especially single story homes. With the stall and amount of rain forecast, you have a pretty good shot at ending up dead whether you cut a hole in the roof of your house or not. GTFO now.

Single story or not - get out. A two story house has more wind resistance and is more likely to take damage from wind. If your house is on stilts, you're getting wind beneath the house, creating upward pressure.

The flooding isn't your only risk. If you're near the coast and in the path, get out.

Ugh. I live in upstate SC (upper left corner of the state on a map) and just the rain is going to be brutal. This is hilly terrain encompassing the lower end of the Blue Ridge mountains, with heavy Piedmont clay ultisol, that's already close to saturated with our normal amount of rainfall so far. I work in the foothills and lower mountains frequently and I know many valleys and river banks are going to be drowned. Wouldn't surprise me at all if several bridges I go over regularly get washed out. The coastal areas are all rightly concerned about the direct damage by wind, flooding, and storm surges (not to mention erosion of the extremely desirable sandy beaches and barrier islands). But inland flooding is going to be an issue in all corners of the Carolinas.

Yup, had an online friend who was in Myrtle Beach SC on Saturday reach out for advice, I told them the only safe plan was to head West of the Appalachian mountains. At the time models were too far out to call North or South movement but it looked certain that the entire Carolinas was going to get soaked hard on top of already saturated soil which will make any low lying area big enough for an RV park susceptible to flooding.

Ok so now I feel bad. Over the last couple days I have gotten more and more relieved because the original tracks had it coming up through south eastern virginia. Each day the updated tracks pushed it further and further west which is a good thing for our area.

It stalling and meandering over the carolinas is going to create a world of hurt for people just south of us.

Yeah, ditto. I'm in NoVA, and was watching the early forecasts with trepidation. They've kept getting better for me personally, but I know there are still going to be people who get killed by this storm, and the current track has a good chance of increasing the number of casualties.

Ok so now I feel bad. Over the last couple days I have gotten more and more relieved because the original tracks had it coming up through south eastern virginia. Each day the updated tracks pushed it further and further west which is a good thing for our area.

It stalling and meandering over the carolinas is going to create a world of hurt for people just south of us.

Hurricanes create a moral quandary - hope for your own safety by basically putting someone north or south of you at risk.

The risk of flooding reminds me of a video that I recently watched about how rich cities are building high levees along rivers, which worsens the flooding for poorer cities with lower levees. I don't know exactly how widespread this problem is, but it probably deserves much more coverage than it gets.

This shows that water and flood management isn't a local issue and should be tackled at the state or even federal level in order to avoid situations where a rich town that can afford a levee causes additional problems in poorer ones without levees. Of course, the question is, can this be addressed on a larger scale. Is there the political interest and political will to get the Army Corps of Engineers involved in order to get things done? It'll also mean increased federal spending which at the moment might not be a welcome thing.